Process for the preparation of polyalkenyl succinic anhydrides

ABSTRACT

A polyalkenyl succinic anhydride is prepared with low amounts of resinous or chlorinated byproducts in a two-step process whereby a polyalkene is first reacted with an unsaturated organic acid in a thermal ene reaction, followed with exposure to a gaseous halogen in presence of an additional amount of the unsaturated organic acidic reagent. The foregoing process produces a polyisobutenyl succinic anhydride having a high ratio of succinic anhydride functional groups to polyisobutenyl backbone groups. Such a polyisobutenyl succinic anhydride is particular suitable for the production of oil-soluble hydrocarbyl succinimides that have good dispersant properties when added to lubricating oil compositions.

TECHNICAL FIELD

The present disclosure relates to the chemical synthesis of polyalkenyl succinic anhydrides suitable as intermediate compounds for the preparation of petroleum product additives, as well as petroleum product additives that may be made from such intermediate compounds.

BACKGROUND AND SUMMARY

Polyalkenyl succinic anhydrides are widely used in the petroleum product industry as precursor compounds for the production of hydrocarbyl polyalkenyl succinimides. Hydrocarbyl polyalkenyl succinimides may be used as detergents in fuel mixtures to reduce engine deposits and as dispersants in lubricating oil compositions to aid in the suspension of particulate matter, additionally having the property of modifying the fluidity of a lubricating oil composition. An example of a polyalkenyl succinic anhydride suitable as such a precursor compound for making lubricating oil additives is polyisobutenyl succinic anhydride (“PIBSA”). PIBSA is usually produced by following either of two conventional processes. For the purposes of simplicity, reference will be made to the process for PIBSA, however the disclosure is intended to relate to processes for the production of all hydrocarbyl polyalkenyl/acid compounds not just PIBSA.

The first process consists of a direct thermal condensation reaction between maleic anhydride and polyisobutene (“PIB”) and is often referred in the art as the “thermal ene” reaction. In the thermal ene reaction, a carbon-carbon bond is formed between an alpha-carbon on the unsaturated organic acidic reagent and a vinylic carbon at a terminus of the polyalkene. Sustained exposure to elevated temperatures above 150° C. is required to obtain good reaction yields, usually for a time period ranging from about 1 to about 48 hours. However, high reaction temperatures typically lead to the formation of a sedimentous resin which is believed to be due to the polymerization and/or decomposition of maleic anhydride. The formation of such insoluble resin or sediment in significant amounts requires a filtration stage before the PIBSA can be used as an additive or as an intermediate in the preparation of other products such as hydrocarbyl succinimides. Furthermore, according to U.S. Pat. No. 5,644,001, undesirable resins in the product introduce not only a significant discrepancy between the real and apparent succinylation in the maleinised product (due to the presence of resinified and/or unreacted maleic anhydride) but also adversely affect the detergency properties of such additives.

In the second type of process, chlorination of the PIB is first carried out, followed by the condensation of the chlorinated PIB with maleic anhydride. This process can be carried out at lower temperature than the thermal ene reaction process, with high yield and without the formation of substantial amounts of sediment. However, the PIBSA obtained with this process contains residual chlorine. Environmental concerns related to chlorine-containing materials and the potential for formation of hazardous byproducts, such as dioxins, that may arise under the conditions prevalent in an internal combustion engine make the use of the second process undesirable. Furthermore, chlorine is also known to be a poison for the catalysts used for exhaust gas treatment systems, i.e. as in catalytic converters.

The aforementioned conventional methods for the preparation of PIBSA tend to involve side reactions that produce tars, resins, or halogenated byproducts which must be separated from the PIBSA before further processing occurs. Undesirable resinous byproducts and reduced product succination are more prevalent when the ene reaction is conducted at elevated temperatures and the polyalkenyl compounds have number average molecular weights above about 1200. Accordingly, there remains a need for an improved synthesis process for relatively highly succinated polyalkenyl succinic anhydrides of relatively high number average molecular weight that does not produce undesirable byproducts during the course of the reaction and does not require extreme reaction conditions such as prolonged heating, elevated pressure, or the presence of a strong acid.

In accordance with a first aspect, an exemplary embodiment of the present disclosure provides a process for making a polyalkenyl succinic anhydride, such as PIBSA. A mixture of highly reactive PIB and maleic anhydride are heated until at least about 50 weight % of the PIB is converted to PIBSA. An additional amount of maleic anhydride is added to the mixture which is subsequently contacted with chlorine gas to convert at least some of the unreacted PIB to PIBSA under conditions sufficient to inhibit the formation of undesirable resinous or chlorinated byproducts.

In accordance with a second aspect, another embodiment of the present disclosure provides a hydrocarbyl succinimide made from a PIBSA produced by the aforementioned process.

In accordance with a third aspect, a further embodiment of the present disclosure provides a lubricant component comprising a hydrocarbyl succinimide made from a PIBSA produced by the aforementioned process.

As described herein the disclosure provides a two-step process for the preparation of polyalkenyl succinic anhydrides, such as PIBSA, with the resultant product having a relatively high ratio of succinic functional groups to polyalkenyl functional groups, and a relatively low level of undesirable contaminants. This novel process also allows PIBSA with a number average molecular weight greater than about 1000, and up to about 3000, to be synthesized. Higher number average molecular weight and a higher ratio of succinic groups to polyalkenyl groups in a compound such as PIBSA increase the dispersant performance of a dispersant made from the PIBSA when the dispersant is combined in a lubricating oil mixture. Accordingly, a smaller amount of dispersant additive may be used per quantity of lubricating oil composition, thereby reducing the cost of production of the lubricant composition as well as reducing the environmental impact.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The production of an oil-soluble hydrocarbyl succinimide suitable for use as a dispersant lubricant additive begins with the production of a polyalkenyl succinic anhydride. In the present disclosure, the polyalkenyl succinic anhydride is synthesized in a two stage reaction process capable of producing a product having both a relatively high number average molecular weight and a relatively high ratio of succinic to polyalkenyl groups. The first stage of the reaction process employs a thermal ene reaction between a polyalkene compound and an unsaturated organic acidic reagent, until about 50 weight % of the polyalkene has been derivatized. Subsequently, an additional amount of the unsaturated organic acidic reagent and a small amount of a halogen gas are added to the reaction until at least some of the underivatized polyalkene has also been converted to a polyalkenyl succinic anhydride in a second stage of the reaction process.

For such purposes, PIB is suitably employed as the polyalkene compound. It has been found that PIB having a greater than 50 mole % content of terminal double bonds is particularly suitable for this reaction. Such PIB is also referred to as highly reactive PIB (“HR-PIB”). HR-PIB having a number average molecular weight ranging from about 800 to about 5000 is particularly suitable for use in embodiments of the present disclosure.

HR-PIB having a number average molecular weight ranging from about 1000 to about 3000 is particularly suitable for an exemplary embodiment of the present disclosure. Such HR-PIB is commercially available, or can be synthesized by the polymerization of isobutene in the presence of a non-chlorinated catalyst such as boron trifluoride, as described in U.S. Pat. No. 4,152,499 to Boerzel, et al. and U.S. Pat. No. 5,739,355 to Gateau, et al. When used in the aforementioned thermal ene reaction, HR-PIB may lead to higher conversion rates in the reaction, as well as lower amounts of sediment formation, due to increased reactivity.

The unsaturated organic acidic reagent of the disclosed process refers to an unsaturated substituted or non-substituted carboxylic acid reagent, for example maleic or fumaric reactants of the general formula:

wherein X and X′ are the same or different, provided that at least one of X and X′ is a group that is capable of reacting to esterify alcohols, forming amides or amine salts with ammonia or amines, forming metal salts with reactive metals or basically reacting metal compounds, or otherwise functioning as an acylating agent. Typically, X and/or X′ is —OH, —O-hydrocarbyl, —NH₂, and taken together X and X′ can be —O— so as to form an anhydride. Preferably, X and X′ are such that both carboxylic functions can enter into acylation reactions.

Maleic anhydride is a particularly suitable unsaturated acidic reactant. Other suitable unsaturated acidic reactants include electron-deficient olefins such as monophenyl maleic anhydride; monomethyl maleic anhydride, dimethyl maleic anhydride, N-phenyl maleimide and other substituted maleimides; isomaleimides; fumaric acid, maleic acid, alkyl hydrogen maleates and fumarates, dialkyl fumarates and maleates, fumaronilic acids and maleanic acids; and maleonitrile and fumaronitrile.

The halogen gas required for the second stage of the process may be a gas selected from the group consisting of fluorine, chlorine, bromine, or iodine. In an exemplary embodiment, chlorine gas is the preferred halogen gas employed. The amount of halogen gas used in the second stage of the process may vary within relatively wide limits. However, it is desirable to use a molar ratio range of about 0.25 moles to 1.5 moles of halogen gas per mole of HR-PIB or acidic reactant.

In embodiments of the present disclosure, a trace amount of a Lewis acid may be used during the first stage of the process. The Lewis acid does not act as a catalyst for the thermal ene reaction, however it does act to inhibit the self-polymerization of the unsaturated organic acidic reagent into an insoluble resin, as described in U.S. Pat. No. 5,071,919 to DeGonia et al. Lewis acids suitable for use in the present disclosure include aluminum chloride, boron trifluoride, iron(III) chloride, and analogs thereof. A trace amount, as required by the present disclosure, may be a concentration of the Lewis acid ranging from about 20 ppm to about 200 ppm.

In the first stage of the presently disclosed process a mixture of HR-PIB, maleic anhydride in a mole ratio of about 1 mole of HR-PIB to about 2 moles of maleic anhydride, and a trace amount of aluminum chloride are exposed to an elevated temperature ranging from about 150° C. to about 250° C. for a duration of time ranging from about 1 hour to about 48 hours, until about 50 weight % of the HR-PIB has been derivatized with the maleic anhydride.

In the second stage of the process, an additional amount of maleic anhydride is combined with the mixture. The amount of maleic anhydride combined with the mixture in the second stage may range from about 0% to about 50% of the total amount of maleic anhydride used in the process. The additional amount of maleic anhydride is combined with the mixture after about 50 weight % of the HR-PIB has been derivatized. During the second stage of the process, chlorine gas in a molar range from about 0.25 moles to about 1.5 moles per mole of HR-PIB in the mixture is bubbled through the mixture, and HCl gas is devolved and removed from the mixture as it is formed.

The second stage of the process is continued until at least some of the unreacted HR-PIB is also derivatized with the maleic anhydride. Such a process has been shown to provide a PIBSA having a succinic anhydride (“SA”) to PIB ratio up to at least about 1.5. As demonstrated in Example 5, such an SA to PIB ratio is able to be achieved even when the HR-PIB used in the process has a number average molecular weight greater than about 1600.

A PIBSA produced by the aforementioned process is suitable for conversion to an oil-soluble succinimide particularly useful as a dispersant additive for lubricating oil compositions. Conversion of PIBSA to a succinimide is well known in the art and may be accomplished through the reaction of a polyamine with the PIBSA, wherein the polyamine has at least one basic nitrogen in the compound, as described in U.S. Pat. No. 3,215,707 and U.S. Pat. No. 4,234,435. Suitable polyamines may have at least three nitrogen atoms and about 4 to 20 carbon atoms. One or more oxygen atoms may also be present in the polyamine.

A particularly suitable group of polyamines for use in the present disclosure are polyalkylene polyamines, including alkylene diamines. Such polyalkylene polyamines may contain from about 2 to about 12 nitrogen atoms and from about 2 to about 24 carbon atoms. Preferably, the alkylene groups of such polyalkylene polyamines may contain from about 2 to about 6 carbon atoms, more preferably from about 2 to about 4 carbon atoms.

Particularly suitable polyalkylene polyamines are those having the formula: H₂N—(R₁NH)_(a)—H wherein R₁ is a straight- or branched-chain alkylene group having from about 2 to about 6 carbon atoms, preferably about 2 to about 4 carbon atoms, most preferably about 2 carbon atoms, i.e., ethylene (—CH₂CH₂—); and a is an integer from 1 to about 10, preferably 1 to about 4, and more preferably about 3.

Examples of suitable polyalkylene polyamines include, but are not limited to, ethylenediamine, propylenediamine, isopropylenediamine, butylenediamine, pentylenediamine, hexylenediamine, diethylenetriamine, dipropylenetriamine, dimethylaminopropylamine, diisopropylenetriamine, dibutylenetriamine, di-sec-butylenetriamine, triethylenetetraamine, tripropylenetetraamine, triisobutylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, dimethylaminopropylamine, and mixtures thereof.

Particularly suitable polyalkylene polyamines are ethylenediamine, diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine. Most suitable are ethylenediamine, diethylenetriamine, and triethylenetetraamine.

Many of the polyamines suitable for use in the present disclosure are commercially available and others may be prepared by methods which are well known in the art. For example, methods for preparing amines and their reactions are detailed in Sidgewick's “The Organic Chemistry of Nitrogen”, Clarendon Press, Oxford, 1966; Noller's “Chemistry of Organic Compounds”, Saunders, Philadelphia, 2nd Ed., 1957; and Kirk-Othmer's “Encyclopedia of Chemical Technology”, 2nd Ed., especially Volume 2, pp. 99-116.

The hydrocarbyl succinimide produced from the PIBSA made by the aforementioned process has a higher number average molecular weight and a higher ratio of succinimide functional linkages to polyalkene backbone groups than other hydrocarbyl succinimides produced from PIBSA made by conventional processes. Accordingly, the inclusion of a presently disclosed hydrocarbyl succinimide into a lubricant composition may provide a lubricant with improved dispersant characteristics as compared to the dispersant characteristics of lubricant compositions containing hydrocarbyl succinimides having lower SA to PIB ratios or lower number average molecular weights.

EXAMPLES

The following non-limiting examples comparatively illustrate one or more advantages of the presently disclosed process over conventional processes in the production of PIBSA having a high SA to PIB ratio. In the following examples, Examples 3 and 5 are made according to the two step process described herein and provide PIBSA products from HR-PIB having a relatively high SA to PIB ratio in relatively high yield. Examples 1 and 6 illustrate products made using non-highly reactive PIB (non-HR-PIB). Examples 2 and 4 were made by a one-step thermal ene reaction using HR-PIB.

PIB PIBSA Product Example # PIB M_(n) Acid # Activity SA:PIB 1 non-HR-PIB 1250 0.672 68.1% 1.37 2 HR-PIB 1250 0.946 88.1% 1.5 3 HR-PIB 1300 1.070 92.0% 1.8 4 HR-PIB 2100 0.552 80.1% 1.5 5 HR-PIB 2100 0.732 91.5% 1.8 6 non-HR-PIB 2100 0.621 89.1% 1.6

In the first example, a conventional (i.e. non-highly reactive) PIB having a number average molecular weight of about 1250 was reacted using the presently disclosed two stage process for the production of PIBSA, yielding a product having a SA:PIB of 1.37 with an activity of 68.1%.

In Example 2, an HR-PIB having a number average molecular weight of about 1250 was reacted using only the thermal ene process for the production of PIBSA, yielding a product having a SA:PIB of 1.5 with an activity of 88.1%.

In Example 3, an HR-PIB having a number average molecular weight of about 1300 was reacted using the presently disclosed two stage process for the production of PIBSA, yielding a product having a SA:PIB of 1.8 with an activity of 92.0%.

In Example 4, an HR-PIB having a number average molecular weight of about 2100 was reacted using only the thermal ene process for the production of PIBSA, yielding a product having a SA:PIB of 1.5 with an activity of 80.1%.

In Example 5, an HR-PIB having a number average molecular weight of about 2100 was reacted using the presently disclosed two stage process for the production of PIBSA, yielding a product having a SA:PIB of 1.8 with an activity of 91.5%.

In Example 6, a conventional PIB having a number average molecular weight of about 2100 was reacted using a chlorination step followed by a thermal reaction yielding a PIBSA having a SA:PIB of 1.6 with an activity of 89.1%.

As demonstrated by the foregoing example, a PIBSA made by the disclosed two step process using an HR-PIB provides products having SA:PIB ratios above about 1.5 and higher activity than conventional processes or processes using non-highly reactive PIB. Another advantage of the disclosed process is that higher molecular weight polyalkenyl compounds may be used without an increase in undesirable byproducts.

At numerous places throughout this specification, reference has been made to a number of U.S. patents and publications. All such cited documents are expressly incorporated in full into this disclosure as if fully set forth herein.

The foregoing disclosed embodiments are susceptible to considerable variation in practice. Accordingly, the embodiments are not intended to be limited to the specific exemplifications set forth hereinabove. Rather, the foregoing embodiments are within the spirit and scope of the appended claims, including the equivalents thereof available as a matter of law.

The patentees do not intend to dedicate any disclosed embodiments to the public, and to the extent any disclosed modifications or alterations may not literally fall within the scope of the claims, they are considered to be part hereof under the doctrine of equivalents. 

1. A process for the preparation of a polyalkenyl succinic acid or anhydride comprising: heating a mixture of a highly reactive polyalkene compound and an unsaturated acidic reagent to a thermal ene reaction temperature until about 50 weight percent of the polyalkene compound has reacted; and subsequently, contacting the mixture with an additional amount of the unsaturated acidic reagent in the presence of a halogen gas to convert at least a portion of unreacted polyalkene compound in the mixture to the polyalkenyl succinic acid or anhydride; wherein the highly reactive polyalkene compound comprises a polyalkene having greater than 50 mole % terminal double bond content.
 2. The process of claim 1 wherein the highly reactive polyalkene compound comprises a polyalkene having a number average molecular weight ranging from about 800 to about
 5000. 3. The process of claim 1 wherein the highly reactive polyalkene compound comprises a polyisobutene having a number average molecular weight ranging from about 1000 to about
 3000. 4. The process of claim 1 wherein the unsaturated acidic reagent is selected from the group consisting of: maleic anhydride, monophenyl maleic anhydride, monomethyl maleic anhydride, dimethyl maleic anhydride, N-phenyl maleimide, a substituted maleimide, an isomaleimide, fumaric acid, maleic acid, an alkyl hydrogen maleate, an alkyl hydrogen fumarate, a dialkyl fumarate, a dialkyl maleate, fumaronilic acid, maleanic acid, maleonitrile, and fumaronitrile.
 5. The process of claim 1 wherein the step of heating further comprises adding a Lewis acid selected from the group consisting of aluminum chloride, boron trifluoride, and iron (III) chloride.
 6. The process of claim 5 wherein the Lewis acid is present in a concentration ranging from about 20 ppm to about 200 ppm.
 7. The process of claim 1 wherein the temperature ranges from about 150° C. to about 250° C.
 8. The process of claim 1 wherein the mixture comprises unreacted polyalkene, unreacted unsaturated acidic reagent, and a polyalkenyl derivative of the unsaturated acidic reagent.
 9. The process of claim 1 wherein the halogen gas is selected from the group consisting of fluorine, chlorine, bromine, and iodine.
 10. The process of claim 1 wherein the halogen gas is present in a molar range from about 0.25 moles to about 1.5 moles per mole of highly reactive polyalkene compound.
 11. A method for making a hydrocarbyl succinimide from the polyisobutenyl succinic anhydride of claim 1 comprising reacting the polyisobutenyl succinic anhydride with a polyamine having at least one basic nitrogen atom.
 12. A method for making a dispersant lubricant additive comprising: heating a mixture of a highly reactive polyalkene compound and an unsaturated acidic reagent to a thermal ene reaction temperature until about 50 weight percent of the polyalkene compound has reacted; and subsequently, contacting the mixture with an additional amount of the unsaturated acidic reagent in the presence of a halogen gas to convert at least a portion of unreacted polyalkene compound in the mixture to the polyalkenyl succinic acid or anhydride; reacting the polyisobutenyl succinic acid or anhydride with a polyamine having at least one basic nitrogen atom, forming a hydrocarbyl succinimide; wherein the highly reactive polyalkene compound comprises a polyalkene having greater than 50 mole % terminal double bond content.
 13. The method of claim 12 wherein the highly reactive polyalkene compound comprises a polyalkene having a number average molecular weight ranging from about 800 to about
 5000. 14. The method of claim 12 wherein the highly reactive polyalkene compound comprises a polyisobutene having a number average molecular weight ranging from about 1000 to about
 3000. 15. The method of claim 12 wherein the unsaturated acidic reagent is selected from the group consisting of: maleic anhydride, monophenyl maleic anhydride, monomethyl maleic anhydride, dimethyl maleic anhydride, N-phenyl maleimide, a substituted maleimide, an isomaleimide, fumaric acid, maleic acid, an alkyl hydrogen maleate, an alkyl hydrogen fumarate, a dialkyl fumarate, a dialkyl maleate, fumaronilic acid, maleanic acid, maleonitrile, and fumaronitrile.
 16. The method of claim 12 wherein the step of heating further comprises adding a Lewis acid selected from the group consisting of aluminum chloride, boron trifluoride, and iron (III) chloride.
 17. The method of claim 16 wherein the Lewis acid is present in a concentration ranging from about 20 ppm to about 200 ppm.
 18. The method of claim 12 wherein the temperature ranges from about 150° C. to about 250° C.
 19. The method of claim 12 wherein the mixture comprises unreacted polyalkene, unreacted unsaturated acidic reagent, and a polyalkenyl derivative of the unsaturated acidic reagent.
 20. The method of claim 12 wherein the halogen gas is selected from the group consisting of fluorine, chlorine, bromine, and iodine.
 21. The method of claim 12 wherein the halogen gas is present in a molar range from about 0.25 moles to about 1.5 moles per mole of highly reactive polyalkene compound. 